condo conversion nightmare

[Condo guy]

What is the name of your state? MA


This is my first post so please forgive my rambling.

I purchased a condo about sixteen months ago. The unit is a conversion. The seller split her house in half and kept the other unit for herself. My unit consists of the first floor and the finished basement. Recently the seller was told by the city/town that a railing needed to be put up outside on the front steps to help bring the conversion up to code. The seller insists that I should incur half the cost. My question is am I legally obligated to pay for any changes required to bring the conversion up to code?
I also would like to add that after the home inspection I submitted a list of things to be done before the purchase date. The seller agreed to fix the things on the list but has yet to do any of the things I requested. I know I didn't have to sign the papers and move in but as a first time owner I was too excited to worry about it at the time. (sucker!)
I thought I read somewhere that for a conversion to be legal or "up to code" it had to have seperate utilities. There is still only one water meter for the house which ended up in my name. The seller in withholding payment from the last water and sewer and bill I paid saying I owe her money for the railing. Can she do this? If I am in the wrong I will certainly do the right thing and honor my obligations. Along those same lines I also thought that there was supposed to be a sperate electrical panel for any common areas that have electricity. (front and back halls, outside lights) There are two panels but I couldn't tell whose service the common areas are linked to. Now I haven't said anything about these issues because I'm not sure if this information is correct and I was content to let things be. Not anymore. Any advice or legal information will be hugely appreciated. Thank you very much.What is the name of your state?